Copper-alloy capping layers for metallization in touch-panel displays

Abstract

In various embodiments, electronic devices such as touch-panel displays incorporate interconnects featuring a conductor layer and, disposed above the conductor layer, a capping layer comprising an alloy of Cu and one or more refractory metal elements selected from the group consisting of Ta, Nb, Mo, W, Zr, Hf, Re, Os, Ru, Rh, Ti, V, Cr, and Ni.

What is claimed is: 
     
       1. A touch-panel display comprising:
 a substrate; 
 a plurality of conductive touch-panel row sensors (i) arranged in lines extending along a first direction and (ii) disposed over the substrate; 
 a plurality of conductive touch-panel column sensors (i) arranged in lines extending along a second direction and intersecting the lines of the row sensors and (ii) disposed over the substrate; and 
 an interconnect (i) disposed at a point of intersection between a line of row sensors and a line of column sensors, and (ii) electrically connecting two column sensors or two row sensors, 
 wherein the interconnect comprises:
 (i) a conductor layer comprising at least one of Cu, Ag, Al, or Au, and 
 (ii) disposed on the conductor layer, a capping layer comprising an alloy of Cu and one or more refractory metal elements selected from the list consisting of Ta, Nb, Mo, W, Zr, Hf, Re, Os, Ru, Rh, Ti, V, Cr, and Ni; and 
 
 wherein (i) the capping layer comprises a plurality of crystalline grains separated by grain boundaries, (ii) at least one of the grain boundaries comprises a particulate therein, and (iii) the particulate comprises an agglomeration of at least one of the refractory metal elements. 
 
     
     
       2. The touch-panel display of  claim 1 , wherein the interconnect extends over or under a row sensor and electrically connects two column sensors, and further comprising an insulating layer disposed between the interconnect and the row sensor and electrically insulating the interconnect and the row sensor. 
     
     
       3. The touch-panel display of  claim 1 , wherein the interconnect extends over or under a column sensor and electrically connects two row sensors, and further comprising an insulating layer disposed between the interconnect and the column sensor and electrically insulating the interconnect and the column sensor. 
     
     
       4. The touch-panel display of  claim 1 , wherein the substrate comprises an insulating material. 
     
     
       5. The touch-panel display of  claim 1 , wherein the substrate comprises glass. 
     
     
       6. The touch-panel display of  claim 1 , wherein the row sensors and column sensors comprise a substantially transparent conductive material. 
     
     
       7. The touch-panel display of  claim 1 , wherein the row sensors and column sensors comprise indium tin oxide. 
     
     
       8. The touch-panel display of  claim 1 , wherein the capping layer comprises an alloy of Cu, Ta, and Cr. 
     
     
       9. The touch-panel display of  claim 8 , wherein the capping layer consists essentially of 1 weight %-12 weight % Ta, 1 weight %-5 weight % Cr, and the balance Cu. 
     
     
       10. The touch-panel display of  claim 8 , wherein the capping layer consists essentially of approximately 5 weight % Ta, approximately 2 weight % Cr, and the balance Cu. 
     
     
       11. The touch-panel display of  claim 8 , wherein the capping layer consists essentially of approximately 2 weight % Ta, approximately 1 weight % Cr, and the balance Cu. 
     
     
       12. The touch-panel display of  claim 1 , wherein the capping layer comprises an alloy of Cu, Ta, and Ti. 
     
     
       13. The touch-panel display of  claim 12 , wherein the capping layer consists essentially of 1 weight %-12 weight % Ta, 1 weight %-5 weight % Ti, and the balance Cu. 
     
     
       14. The touch-panel display of  claim 12 , wherein the capping layer consists essentially of approximately 5 weight % Ta, approximately 2 weight % Ti, and the balance Cu. 
     
     
       15. The touch-panel display of  claim 1 , wherein the capping layer comprises an alloy of Cu, Nb, and Cr. 
     
     
       16. The touch-panel display of  claim 15 , wherein the capping layer consists essentially of 1 weight %-10 weight % Nb, 1 weight %-5 weight % Cr, and the balance Cu. 
     
     
       17. The touch-panel display of  claim 15 , wherein the capping layer consists essentially of approximately 5 weight % Nb, approximately 2 weight % Cr, and the balance Cu. 
     
     
       18. The touch-panel display of  claim 1 , wherein (i) the interconnect comprises a sidewall comprising (a) an exposed portion of the capping layer, (b) an exposed portion of the conductor layer, and (c) an interface between the exposed portion of the capping layer and the exposed portion of the conductor layer, and (ii) the sidewall of the electrode is substantially free of discontinuities notwithstanding the interface. 
     
     
       19. The touch-panel display of  claim 1 , wherein the capping layer comprises an alloy of Ta and Cu. 
     
     
       20. The touch-panel display of  claim 1 , wherein the capping layer comprises an alloy of Nb and Cu. 
     
     
       21. The touch-panel display of  claim 1 , wherein the capping layer comprises an alloy of Ta, Zr, and Cu. 
     
     
       22. A method of forming an interconnect of a touch-panel display, the method comprising:
 providing a structure comprising (i) a substrate, (ii) a plurality of conductive touch-panel row sensors (a) arranged in lines extending along a first direction and (b) disposed over the substrate, and (iii) a plurality of conductive touch-panel column sensors (a) arranged in lines extending along a second direction and intersecting the lines of the row sensors and (b) disposed over the substrate; 
 depositing an insulator layer at least at a point of intersection between a line of row sensors and a line of column sensors; 
 depositing over the insulator layer a conductor layer comprising at least one of Cu, Ag, Al, or Au; 
 depositing over the conductor layer a capping layer comprising an alloy of Cu and one or more refractory metal elements selected from the group consisting of Ta, Nb, Mo, W, Zr, Hf, Re, Os, Ru, Rh, Ti, V, Cr, and Ni, wherein the capping layer comprises a plurality of crystalline grains separated by grain boundaries; 
 forming a mask layer over the capping layer; 
 patterning the mask layer to reveal a portion of the capping layer, a remaining portion of the mask layer at least partially defining a shape of the interconnect; 
 applying an etchant to remove portions of the capping layer and the conductor layer not masked by the patterned mask layer, thereby forming a sidewall of the interconnect (a) comprising (i) an exposed portion of the capping layer, (ii) an exposed portion of the conductor layer, and (iii) an interface between the exposed portion of the capping layer and the exposed portion of the conductor layer, and (b) substantially free of discontinuities notwithstanding the interface; and 
 annealing the interconnect at a temperature sufficient to form a particulate within at least one of the grain boundaries, the particulate comprising an agglomeration of at least one of the refractory metal elements. 
 
     
     
       23. The method of  claim 22 , wherein the etchant comprises a mixture of phosphoric acid, acetic acid, nitric acid, and water. 
     
     
       24. The method of  claim 22 , wherein the etchant consists essentially of 50-60 weight % phosphoric acid, 15-25 weight % acetic acid, 3-5 weight % nitric acid, and the balance water. 
     
     
       25. The method of  claim 22 , wherein the etchant consists essentially of 50 weight % phosphoric acid, 25 weight % acetic acid, 3 weight % nitric acid, and the balance water. 
     
     
       26. The method of  claim 22 , wherein the capping layer comprises an alloy of Cu, Ta, and Cr. 
     
     
       27. The method of  claim 22 , wherein the capping layer comprises an alloy of Cu, Ta, and Ti. 
     
     
       28. The method of  claim 22 , wherein the capping layer comprises an alloy of Cu, Nb, and Cr. 
     
     
       29. The method of  claim 22 , wherein the capping layer comprises an alloy of Ta and Cu. 
     
     
       30. The method of  claim 22 , wherein the capping layer comprises an alloy of Nb and Cu. 
     
     
       31. The method of  claim 22 , wherein the capping layer comprises an alloy of Ta, Zr, and Cu.